1. Field of the Invention
The present invention relates to an optical tomographic imaging apparatus, and particularly to an optical tomographic imaging apparatus used in opthalmologic diagnosis and treatment and the like.
2. Description of the Related Art
Various opthalmologic devices that utilize optical devices are in use today.
For example, various devices such as an anterior ocular segment photographing device, a fundus camera, and a scanning laser opthalmoscope (SLO) are used as optical devices for observing the eye.
Among such optical devices, an optical tomographic imaging apparatus based on optical coherence tomography (hereinafter referred to as OCT) that utilizes multi-wavelength lightwave interference is capable of obtaining a high-resolution tomographic image of a sample.
OCTs are becoming indispensable opthalmologic devices at outpatient retina specialists.
According to the optical tomographic imaging apparatus described above, when a sample is irradiated with a measuring beam that is a low-coherence light, a backscattering light from the sample can be measured at high sensitivity by using an interference system.
In addition, by scanning the measuring beam on the sample, the optical tomographic imaging apparatus can obtain a high-resolution tomographic image.
Therefore, since an optical tomographic imaging apparatus is also capable of high-resolution tomographic imaging of a retina in a fundus of an eye to be inspected, optical tomographic imaging apparatuses are widely used in opthalmologic diagnosis and treatment of retinas.
In recent years, with opthalmologic optical tomographic imaging apparatuses, a transition is underway from conventional time domain optical coherence tomography to Fourier domain optical coherence tomography that enables imaging at higher speeds.
While information is acquired per a specific depth in an eye to be inspected in time domain optical coherence tomography, since Fourier domain optical coherence tomography collectively acquires information in a depth direction, high-speed imaging can be performed.
High-speed imaging enables the prevention of image blur and image loss due to ocular movement represented by involuntary eye movement.
On the other hand, conventionally, an optical apparatus is proposed in Japanese Patent Application Laid-Open No. 2002-174769 in order to satisfy both demands for higher resolution and for reductions in imaging time.
Specifically, an optical apparatus for observing the inside of a biological specimen is proposed which uses both OCT and OCM (optical coherence microscopy) as the situation demands.
The apparatus is configured to use OCT when verifying large structures in a biological specimen and to be switchable to OCM when further observing an attention area in the biological specimen at a higher resolution.
In doing so, since OCT and OCM significantly differ from each other in depth of focus (DOF), the apparatus is configured using a beam diameter conversion optical system so that beam diameters respectively corresponding to OCT having a small numerical aperture and OCM having a large numerical aperture can be set.
Accordingly, observations can be performed at a high S/N ratio.
In addition, Japanese Patent Application Laid-Open No. 2007-101250 proposes an optical tomographic imaging apparatus arranged such that high resolution is achieved by OCT itself due to Fourier domain optical coherence tomography.
The apparatus is arranged so that in order to compensate for a narrow depth of focus (DOF), an optical path length adjustment unit is used to move a focusing position of a measured object in a depth direction to obtain a plurality of images, and the plurality of images is combined to acquire high-resolution tomographic images of the measured object in a horizontal direction and an optical axis direction.